Typical oilfield connections rely on rotation to screw individual threaded components together. The make-up of these relative rotation connections requires that one or both components undergo rotational movement while the components are screwed together. This rotational movement does not prohibit axial alignment along the centerline of the components during make-up, but it does prohibit axial alignment at any off-center location during the make-up process. This severely limits the number of separate ports/passages into the adjoining components available for wireline or hydraulic communication use. For example, consider the use of a relative rotation based threaded connection between two components, each of which includes a wireline port that passes continuously therethrough at a location 2.54 cm (1 inch) off-center, and through which a wireline is disposed. During the make-up process, relative rotation between the two components causes the wireline ports to rotate in opposite directions along a circular path relative to each other, thus shearing the wireline. Although relative rotation type threaded connections provide high strength with minimal use of a cylindrical cross-section, off-center axial alignment is not possible during make-up.
Typical down-hole connections such as rotary shouldered connections, e.g., API numbered connections, AMERICAN MT, HUGHES H-90, and REED FULL HOLE, all of which are familiar to those skilled in the art, utilize a pin and box connection requiring relative rotational movement.
Stab type pin and box connections which rely on some type of retaining pins or screws to hold the connection together, as is familiar to those skilled in the art, allow for a rotation free connection but lack the strength needed for many down-hole applications, and take up much needed cross sectional area.
Connections are available that do not use relative rotation threaded connections, and thus allow axial alignment during the connection make-up process. In these connections, axial alignment is typically enabled by using a collar that screws onto only one of the mating components. The other mating component has a non-thread type connection that allows the collar to spin freely during the make-up process. Consequently, the non-threaded end requires a sub-optimal connection that necessarily requires a larger fraction of the available cross-sectional area to provide the required strength. This limits the available cross-sectional area for non-connection related engineering purposes, and thus requires a larger diameter design to accommodate the required engineering features, i.e., uses a large footprint design. In most cases a large footprint design dramatically decreases the utility of the engineered component in down-hole applications, and in many cases renders the component unusable.
A need exists for threaded connections that can be made-up while off-center alignment of connected components is maintained. An objective of this invention is to provide such threaded connections and methods of making same.